Method of automatic control of the discharge of a concentrated traction of solid particles dispersed in liquids from a centrifuge rotor

ABSTRACT

The control of discharge valves for the discharge of a concentrate from the circumference of a centrifuge rotor is achieved by application of an elastically yieldable body, elongated and shortened in accordance with the increasing and decreasing level of the concentrate in the circumferential part of the centrifuge body.

United States Patent [1 1 Putterlik 1451 July 31,1973

METHOD OF AUTOMATIC CONTROL OF THE DISCHARGE OF A CONCENTRATED TRACTIONOF SOLID PARTICLES DISPERSED IN LIQUIDS FROM A CENTRIFUGE ROTOR JanPutterllk, Praha, Czechoslovakia Ceskoslovenska akademie ved, Praha,Czechoslovakia Filed: Jan. 3, 1972 Appl. No.: 214,662

Inventor:

Assignee:

Foreign Application Priority Data Jan. 18, 1971 Czechoslovakia 330 US.Cl. 233/47 R, 137/510 Int. Cl 1104b 11/00 Field of Search 233/19 R, 19A, 20 R,

[56] References Cited UNITED STATES PATENTS 3,341,093 9/1967 Putterlik233/20 R 2,365,752 12/1944 Edwards 137/510 X 2,623,535 12/1952 Morgan137/510 X 2,173,579 9/1939 Fawcett 233/20 R 3,114,655 1211963 Jiskra233/20 R Primary Examiner-George H. Krizmanich Atmrney- Richard Low andMurray Schaffer [57] ABSTRACT The control of discharge valves for thedischarge of a concentrate from the circumference of a centrifuge rotoris achieved by application of an elastically yieldable body, elongatedand shortened in accordance with the increasing and decreasing level ofthe concentrate in the circumferential part of the centrifuge body.

4 Claims, 3 Drawing Figures PAIENIEU l 3 I m sum 1 (If 2 METHOD OFAUTOMATIC CONTROL OF THE DISCHARGE OF A CONCENTRATED TRACTION OF SOLIDPARTICLES DISPERSED IN LIQUIDS FROM A CENTRIFUGE ROTOR BACKGROUND OF THEINVENTION This invention relates to a method of automatic discharge of aconcentrated fraction of solid particles dispersed in liquids from therotor of a centrifuge by means of discharge valves and to an arrangementfor execution of this method, comprising discharge valves with valverods, the position of which is controlled by automatic regulators.

Actually used methods for the discharge of concentrated fractions ofdispersions of solid particles in liquids by means of independentlyoperating regulators from a centrifuge rotor are generally based on theprinciple of a hydraulic actuation of the discharge valves.

So far this hydraulic drive of discharge valves is controlled accordingto a program, for instance within time intervals, it is impossible toachieve a perfect conformity of volumes of the produced and dischargedconcentrated fraction. in order to prevent any excessive deposit of theconcentrated fraction in the centrifuge rotor, a larger volume has to bedischarged than is produced so that also a part of a not concentratedfraction is discharged, reducing thus the efficiency of concentrating.

More progressive methods are based on the dependence of the hydrostaticpressure on the concentration of the centrifuged dispersion, or on thechanges of volume of the concentraged fraction at an increasing anddecreasing level of the concentrate in the centrifuge rotor. But thesedischarge methods still have drawbacks in a reduced efficiency of thedischarge and a reduced output. This is caused by the circumstance, thata constantly adjusted hydraulic drive of valve rods is actuated notsolely by pressure or changes of volume of the concentrated fraction,but also by the pressure of the centrifuged dispersion in the spacecentripetally above the concentrate. This pressure varies considerablydue to different irregularities of the operation as for instance due tovariations of passage of the dispersion and of the counterpressure ofthe separated fraction, influencing'unfavourably the operation of thevalves and the uniformity of concentration of the dishchargedconcentrated fraction.

It isan object ofthis invention to eliminate these drawbacks and toprovide an automatic control of the discharge of the concentratedfraction from the centrifuge rotor through discharge valves independence on the increasing and decreasing level of the concentrate.

It is another object of this invention to eliminate or at least tosubstantially reduce the influence of the dispersion which iscentripetally above the concentrate on the discharge of the concentrate.

SUMMARY OF THE INVENTION According to this invention the opening andclosing of discharge valves is derived from changes of the shape of anelastically yieldable body, situated within the range of radial changesof the lower and .upper level of the concentrate in the rotor, whichbody is elongated and shortened in the radial direction of thecentrifuge rotor due to increasing and decreasing centrifugal pressureof the concentrate, whereby the influence of pressure of the treateddispersion, which is centripetally above the level of the concentrate,on the elastically yieldable body is eliminated by using a material forsaid body, the volume compressibility of which corresponds to the volumecompressibility of liquids.

A notable improvement in the control of discharge valves is therebyachieved, as due to the circumstance that this operation is derivedsolely from pressure differences caused by variations between an upperand lower level of the concentrate in the centrifuge rotor and byelimination of influences of any pressure variations of the dispersionwhich is centripetally above the concentrate, a discharge of such avolume of the concentrated fraction is secured, which correspondsexactly to the produced amount of concentrate. Another advantage of thiscontrol is, that the regulators required for this control are simple andreliable, using an elastically yieldable body.

Each of these regulators may comprise an elastically yieldable body,capable to be extended and shortened in the radial direction ofcentrifuge rotor, the volume compressibility of which body correspondsto the volume compressibility of liquids, which body is anchored withits end distant from the rotor axis in a bracket of the centrifuge rotorand which is provided on its end closer to the rotor axis with a strappiece, on which a valve rod is suspended, passing through the axis ofthe elastically yieldable body.

A substantially simple embodiment of the object of this invention isthus created which is efficient, cheap in manufacture, easy to maintainand particularly reliable in operation as the major parts of theregulator consist of the elastically yieldable body with a valve rodpassing through said body.

DESCRIPTION OF DRAWINGS An exemplary embodiment of the object of thisinvention is indicated in the attached drawings, where FIG. 1 shows aare rotor in a section perpendicularly to its rotation axis,

FIGS. 2 and 3 ar longitudinal sectional views of regulators showing aclosed and an open valve.

DESCRIPTION OF PREFERRED EMBODIMENT In FIG. 1 we see a simplified viewof part of a centrifuge rotor 1 in a section perpendicularly to therotation axis of this rotor, passing through the discharge valves 2. Thecentrifuge space 3 with a not shown centrifuge separator, for instancewith a disk separator occupies the central part of the rotor 1, having asupply and a discharge of the centripetally separated fraction. Aconcentration space 4 occupies the circumferential part of the rotor 1,whichspace is subdivided into a number of sector compartments A, B, C, Dwhere the concentrated fraction is settling, the upper level of whichconcentrated fraction is indicated by a cylindrical surface of theradius R and its lower. level by a cylindrical surface of the radius REach sector compartment A, B of the concentrating space 4 terminates inthe radial direction from the rotor axis in a discharge valve 2, thepassage through which is controlled by a regulator 5. Each regulator 5consists of an elastically yieldable body 6, a stiff strap piece 7, avalve rod 8 and a bracket 9.

The elastically yieldable body 6 is with its end distant from the axisof the centrifuge rotor I inserted and anchored in a bracket 9, fixed inthe rotor 1. This elastically yieldable body 6 must be made of amaterial which is sufficiently elastic so as to return to its originalshape after forces which caused its deformation have ceased and itsvolume should depend on pressure in a negligible way only, similarly asliquids, for which this is a characteristic property.

It is furthermore advisable that the specific weight of the materialfrom which the elastically yieldable body 6 is made, is rather close tothe specific weight of the treated dispersion in the centrifuge space 3.Both these requirements are met for instance by full rubber, the volumecompressibility of which is practically negligible, which is perfectlyelastic and its specific weight can be adjusted by fillers to therequired value. Rubber made from natural rubber without fillers has forinstance a specific weight about 960 kg m, whereby the treateddispersions have generally a higher specific weight and the higherspecific weight can be easily adjusted by fillers.

The automatic control of passage of the concentrate through thedischarge valves 2 according to the described embodiment proceeds asfollows:

The concentrated fraction of the treated dispersion is separated in thecentrifuge space 3 and settles due to centrifugal forces in the cause ofproceeding concentration in the individual sector compartments A, B ofthe concentrating space 4, which sector compartments are filled withconcentrate within the range of its upper level and lower level,determined by cylindrical surfaces of radii R and R So far theconcentrate does not surpass the lower level, determined by acylindrical surface of the radius R,, as indicated for sector B, thesurface of the regulator is exposed to the pressure of the treateddispersion, surrounding the regulator 5 and occupying the centrifugespace 3 centripetally above the concentrate. As the volumecompressibility of the elastically yieldable body 6 is the same as ofliquids, this elastically yieldable body 6 forms an adequate part of thehydraulic content, represented by the treated dispersion. Thecentrifugal pressure of the treated dispersion therefore causes nodeformation of this elastically yieldable body 6 even if it varies dueto not uniform conditions of operation. Therefore so far the level ofthe concentrate does not surpass the lower value determined by acylindrical surface of a radius R, shown in sector B in FIG. 1 and inFIG. 2, the discharge valve 2 remains closed by the valve rod 8 of theregulator 5. If however the level of the settled concentrate rises abovethe lower valve determined by the radius R it starts to surround theelastically yieldable body 6 of the regulator 5 and as the specificweight of the concentrate is larger than that of the treated dispersion,which has been displaced by this concentrate, it acts on the elasticallyyieldable body on their contact places with increased pressure andstarts to compress this elastically yieldable body 6 in directiontowards the valve rod 8 at a simultaneous centripetal elongation intothe centrifuge space 3 containing the treated dispersion having a lowerspecific weight and producing therefore a smaller pressure. In sector Cof the concentrating space 4 are in FIG. 1 and FIG. 3 shown conditionshow the increasing amount of the concentrated fraction reached the upperlevel with the cylindrical surface having a radius R, and how theelastically yieldable body 6 has been thereby deformed.

In this case the settled concentrated fraction with a higher specificweight surrounds the elastically yieldable body 6 with a lower specificweight, compresses it perpendicularly to the axis of the regulator 5 andelongates it by hydrostatic pressure, lifting thereby simultaneously thestiff strap piece 7 with the suspended valve rod 8 and opening thus thedischarge valve 2.

The opening of the discharge valve 2 introduces a centrifugal dischargeof the settled concentrated fraction from this sector C from the rotor Iup to a moment where the concentrate drops to the lower level determined by cylindrical surface of the radius R,, where again conditionsindicated in sector B are prevailing, where the regulator 5 issurrounded by the still not concentrated dispersion, the centrifugalpressure of which does not cause any deformation of the elasticallyyieldable body 6, so that this body 6 takes its original shape, loweringthe stiff strap piece 7 with the suspended valve rod 8, which closesagain the discharge valve 2. Thus the centrifugal discharge ceases andthe settled concentrated fraction starts again to rise. The describedcycle is constantly repeated.

In the course of the described operation of the regulator 5, axialmovements of the valve rod 8 passing through the elastically yieldablebody take place, as indicated in FIGS. 2 and 3, whereby both these partsremain in close contact. That is enabled by the capability of a shearingdeformation of the elastically yieldable body 6 which capability is herefully utilized. A perfect tightness of the closed mechanism of theregulator 5 is thereby achieved, where no treated dispersion can enter,so that an operation without failure is safeguarded.

The object of this invention can be used for separating andconcentrating fine grain dispersions of solid materials in liquids suchas are all suspensions and of heavier components in a combination ofliquids. A possibility of extensive application is given by theextraordinary simplicity as shown by the described solution ofregulators 5 with elastically yieldable bodies 6.

It is obvious that the same effect could be obtained with anotherconstructional solution, for instance by suspending the elasticallyyieldable body 6 instead by its supporting on the bracket 9. Similarlysome other material can be used for the elastically yieldable body 6than rubber, for instance a yieldable container filled with a liquid.

I claim:

1. A method of automatic control of the discharge of a concentratedfraction of a dispersion of solid particles in a liquid and of a heaviercomponent in a combination of liquids from a centrifuge rotor bydischarge valves, in dependence on an increasing and decreasing level ofthe concentrate, said method comprising the steps of utilizing for thiscontrol changes of longitudinal dimensions of a solid elasticallyyieldable body which changes being caused by the variations in pressureof an increasing and decreasing level of the concentrate at thecircumference of a centrifuge rotor, simultaneously eliminating theinfluence of the treated nonconcentrated dispersion occupying the rotorspace centripetally from the concentrate on the elastically yieldablebody by employing an elastically yieldable body having a volumecompressibility corresponding to the volume compressibility of theliquids.

2. In a centrifuge comprising a rotor for separating a liquid dispersionof solid particles into a concentrated fraction and a heavier component,an arrangement for the automatic control of the discharge of theconcentrated fraction comprising a plurality of discharge openingssituated at the circumference of the rotor,

LII

movement of said elastically yieldable body.

3. An arrangement as set forth in claim 2 the specific weight of theelastically yieldable body adjusted to the specific weight of thedispersion occupying the space of the centrifuge rotor centripetallyfrom the concentrate.

4. An arrangement as set forth in claim 2, the elastically yieldablebody anchored with its end distant from the rotor axis on a bracket ofthe centrifuge rotor and provided on its end closer to the rotor axiswith a strap piece, on which the valve rod is suspended.

i i 1! l 4

1. A method of automatic control of the discharge of a concentratedfraction of a dispersion of solid particles in a liquid and of a heaviercomponent in a combination of liquids from a centrifuge rotor bydischarge valves, in dependence on an increasing and decreasing level ofthe concentrate, said method comprising the steps of utilizing for thiscontrol changes of longitudinal dimensions of a solid elasticallyyieldable body which changes being caused by the variations in pressureof an increasing and decreasing level of the concentrate at thecircumference of a centrifuge rotor, simultaneously eliminating theinfluence of the treated non-concentrated dispersion occupying the rotorspace centripetally from the concentrate on the elastically yieldablebody by employing an elastically yieldable body having a volumecompressibility corresponding to the volume compressibility of theliquids.
 2. In a centrifuge comprising a rotor for separating a liquiddispersion of solid particles into a concentrated fraction and a heaviercomponent, an arrangement for the automatic control of the discharge ofthe concentrated fraction comprising a plurality of discharge openingssituated at the circumference of the rotor, each opening having anassociate elastically yieldable body mounted to move radially within acircumferential area of said rotor defined by a predetermined upper andlower level of the concentrate, said elastically yieldable body beingmade of solid material having a volume compressibility corresponding tothat of said liquid, thereby to be elongated and shortened in responseto changes in pressure caused the change in concentrate level, and avalve rod embedded in said elastically yieldable body and reciprocallyextending within said opening to open and close said opening on movementof said elastically yieldable body.
 3. An arrangement as set forth inclaim 2 the specific weight of the elastically yieldable body adjustedto the specific weight of the dispersion occupying the space of thecentrifuge rotor centripetally from the concentrate.
 4. An arrangementas set forth in claim 2, the elastically yieldable body anchored withits end distant from the rotor axis on a bracket of the centrifuge rotorand provided on its end closer to the rotor axis with a strap piece, onwhich the valve rod is suspended.